Neoplasia is characterized by deregulated cell growth and division. Inevitably, molecular pathways controlling cell growth must interact with those regulating cell division. It was not until very recently, however, that experimental evidence became available to bring such connection to light. Cyclin A was found in association with the adenovirus oncoprotein E1A in virally transformed cells (Giordona et al. Cell 58:981 (1989); and Pines et al. Nature 346:760 (1990)). In an early hepatocellular carcinoma, the human cyclin A gene was found to be the integration site of a fragment of the hepatitis B virus, which leads to activation of cyclin A transcription and a chimeric viral cyclin A protein that is not degradable in vitro (Wang et al. Nature 343:555 (1990)). The cell-cycle gene implicated most strongly in oncogenesis thus far is the human cyclin D1. It was originally isolated through genetic complementation of yeast G1 cyclin deficient strains (Xiong et al. Cell 65:691(1991); and Lew et al. Cell 66:1197 (1991)), as cellular genes whose transcription is stimulated by CSF-1 in murine macrophages (Matsushine et al. Cell 65:701 (1991)) and in the putative oncogene PRAD1 rearranged in parathyroid tumors (Montokura et al. Nature 350:512 (1991). Two additional human D-type cyclins, cyclins D2 and D3, were subsequently identified using PCR and low-stringency hybridiazation techniques (Inaba et al. Genomics 13:565 (1992); and Xiong et al. Genomics 13:575 (1992)). Cyclin D1 is genetically linked to the bcl-1 oncogene, a locus activated by translocation to an immunoglobulin gene enhancer in some B-cell lymphomas and leukemias, and located at a site of gene amplification in 15-20% of human breast cancers and 25-48% of squamous cell cancers of head and neck origin.
However, the creation of a mutant onocogene is only one of the requirements needed for tumor formation; tumorigenesis appears to also require the additional inactivation of a second class of critical genes: the xe2x80x9canti-oncogenesxe2x80x9d or xe2x80x9ctumor-suppressing genes.xe2x80x9d In their natural state these genes act to suppress cell proliferation. Damage to such genes leads to a loss of this suppression, and thereby results in tumorigenesis. Thus, the deregulation of cell growth may be mediated by either the activation of oncraenes or the inactivation of tumor-suppressing genes (Weinberg, R. A., (September 1988) Scientific Amer. pp 44-51).
Oncogenes and tumor-suppressing genes a basic distinguished feature. The oncogenes identified thus far have arisen only cells, and thus have been incapable of transmitting their effects to the germ line of the host animal. In contrast, mutations in tumor-suppressing genes can be identified in germ line cells, and are thus transmissible to an animal""s progeny.
The classic example of a hereditary cancer is retinoblastomas in children. The incidence of the retinoblastomas is determined by a tumor suppressor gene, the retinoblastoma (RB) gene (Weinberg, R. A., (September 1988) Scientific Amer. pp 44-51; Hansen et al. (1988) Trends Genet 4:125-128). Individuals born with a lesion in one of the RB alleles are predisposed to early childhood development of retinoblastomas. Inactivation or mutation of the second RB allele in one of the somatic cells of these susceptible individuals appears to be the molecular event that leads to tumor formation (Caveneee et al. (1983) Nature 305:799-784; Friend et al. (1987) PNAS 84:9059-9063).
The RB tumor-suppressing gene has been localized onto human chromosome 13. The mutation may be readily transmitted through the germ line of afflicted individuals (Cavenee et al. (1986) New Engl. J. Med 314:1201-1207). Individuals who have mutations in only one of the two naturally present alleles of this tumor-suppressing gene are predisposed to retinoblastoma. Inactivation of the second of the two alleles is, however, required for tumorigenesis (Knudson (1971) PNAS 68:820-823).
A second tumor-suppressing gene is the p53 gene (Green (1989) Cell 56:1-3; Mowat et al (1985Nature 314:633-636). The protein encoded by the p53 gene is a nuclear protein that forms a stable complex with both the SV40 large T antigen and the adenovirus EIB 55 kd protein. The p53 gene product may be inactivated by binding to these proteins.
Based on cause and effect analysis of p53 mutants, the functional role of p53 as a xe2x80x9ccell-cycle checkpointxe2x80x9d, particularly with respect to controlling progression of a cell from G1 phase into S phase, has implicated p53 as able to directly or indirectly affect cycle cyle machinery. The first firm evidence for a specific biochemical link between p53 and the cell-cycle comes a finding that p53 apparently regulates expression of a second protein, p21, which inhibits cyclin-dependent kinases (CDKs) needed to drive cells through the cell-cycle, e.g. from G1 into S phase. For example, it has been demonstrated that non-viral transformation, such as resulting at least in part from a mutation of deletion of the p53 tumor suppressor, can result in loss of p21 from cyclin/CDK complexes. As described Xiong et al. (1993) Nature 366:701-704, induction of p21 in response to p53 represents a plausible mechanism for effecting cell-cycle arrest in response to DNA damage, and loss of p53 may deregulate growth by loss of the p21 cell-cycle inhibitor.
The role of RB as a tumor-suppressor protein in cell-cycle control is believed to be similar to that of p53. However, whereas p53 is generally believed to be responsive to such indigenous environmental cues as DNA damage, the RB protein is apparently involved in coordinating cell growth with exogenous stimulus that normally persuade a cell to cease proliferating, such as diffusible growth inhibitors. In normal cells, RB is expressed throughout the cell cycle but exists in multiple phosphorylated forms that are specific for certain phases of the cycle. The more highly phosphorylated forms are found during S and G2/M, whereas the underphosphorylated forms are the primary species seen in G1 and in the growth arrested state. Base on these observations, it has been argued that if RB is to have a regulatory (suppressive) activity in the cell-cycle, this activity must be regulated at the post-translational level. Accordingly, underphosphorylated RB would be the form with growth-suppressive activity, since this form is prevalent in G1 and growth arrested cells.
To this end, it is noted that various paracrine growth inhibitors, such as members of the TGF-xcex2 family, prevent phosphorylation of RB and arrest cells in late G1. Current models suggest that during G1, cyclin dependent kinases and particularly cyclin D-associated kinases, CDK4 and CDK6, phosphorylate the product of the retinoblastoma susceptibility gene, RB, and thus release cells from its growth inhibitory effects. TGF-xcex2 treatment causes accumulation of RB in the under-phosphorylated state and expression of RB-inactivating viral oncoproteins prevent TGF-xcex2 induced cell cycle arrest. In similar fashion, other related differentiation factors, such as activin, induce accumulation of unphosphorylated RB that is correlated with arrest in G1 phase.
Recently, it has been demonstrated that the RB protein is a phosphorylation substrate for both CDK4 and CDK6 (Serano et al. (1993) Nature 366:704-707; Kato et al. (1993) Genes Dev 7:331-342; and Meyerson et al. (1994) Mol Cell Biol 14:2077-2086). However, prior to the present discovery, there was little information concerning the manner by which CDK phosphorylation of RB was negatively regulated.
The present invention relates to the discovery in eukaryotic cells, particularly mammalian cells, of a novel family of cell-cycle regulatory proteins (xe2x80x9cCCR-proteinsxe2x80x9d). As described herein, this family of proteins includes a polypeptide having an apparent molecular weight of 16 kDa, and a polypeptide having an apparent molecular weight of approximately 15 kDa, each of which can function as an inhibitor of cell-cycle progression, and therefore ultimately of cell growth. Thus, similar to the role of p21 to the p53 checkpoint, the subject CCR-proteins may function coordinately with the cell-cycle regulatory protein, retinoblastoma (RB). Furthermore, the CCR-protein family includes a protein having an apparent molecular weight of 13.5 kDa (hereinafter xe2x80x9cp13.5xe2x80x9d). The presumptive role of p13.5, like p16 and p15, is in the regulation of the cell-cycle.
One aspect of the invention features a substantially pure preparation of a cell cycle regulatory (CCR) protein, or a fragment thereof, the full-length form of the CCR-protein having an approximate molecular weight in the range of 13 to 16.5 kD, preferably 14.5 kD to 16 kD. In preferred embodiments, the full length form of the CCR-protein has an apparent molecular weight of approximately 13.5 kD, 15 kD, 15.5 kD or 16 kD. In a preferred embodiment: the polypeptide has an amino acid sequence at least 60% homologous to the amino acid sequence represented in one of SEQ ID No. 2, 4 or 6; the polypeptide has an amino acid sequence at least 80% homologous to the amino acid sequence represented in one of SEQ ID No. 2, 4 or 6; the polypeptide has an amino acid sequence at least 90% homologous to the amino acid sequence represented in one of SEQ ID No. 2, 4 or 6; the polypeptide has an amino acid sequence identical to the amino acid sequence represented in one of SEQ ID No. 2, 4 or 6. In a preferred embodiment: the fragment comprises at least 5 contiguous amino acid residues of SEQ ID No. 2, 4 or 6; the fragment comprises at least 20 contiguous amino acid residues of SEQ ID No. 2, 4 or 6; the fragment comprises at least 50 contiguous amino acid residues of SEQ ID No. 2, 4 or 6. For instance, the CCR-protein can comprise an amino acid sequence represented by the general formula:
Met-Met-Met-Gly-Xaa-Xaa-Xaa-Val-Ala-Xaa-Leu-Leu-Leu-Xaa-Xaa-Gly-Ala-Xaa-Xaa-Asn-Cys-Xaa-Asp-Pro-Xaa-Thr-Xaa-Xaa-Xaa-Arg-Pro-Val-His-Asp-Ala-Ala-Arg-Glu-Gly-Phe-Leu-Asp-Thr-Leu-Val-Val-Leu-His-Xaa-Xaa-Gly-Ala-Arg-Leu-Asp-Val-Arg-Asp-Ala-Trp-Gly-Arg-Leu-Pro-Xaa-Asp-Leu-Ala-Xaa-Glu-Xaa-Gly-His-Xaa-Asp-Xaa-Xaa-Xaa-Tyr-Leu-Arg-Xaa-Ala-Xaa-Gly (SEQ ID No. 11)
For, example, the CCR-protein can be represented by the sequence:
Met-Asp-Pro-Ala-Ala-Gly-Ser-Ser-Met-Glu-Pro-Ser-Ala-Asp-Trp-Leu-Ala-Thr-Ala-Ala-Ala-Arg-Gly-Arg-Val-Glu-Glu-Val-Arg-Ala-Leu-Leu-Glu-Ala-Val-Ala-Leu-Pro-Asn-Ala-Pro-Asn-Ser-Tyr-Gly-Arg-Arg-Pro-Ile-Gln-Val-Met-Met-Met-Gly-Xaa-Xaa-Xaa-Val-Ala-Xaa-Leu-Leu-Leu-Xaa-Xaa-Gly-Ala-Xaa-Xaa-Asn-Cys-Xaa-Asp-Pro-Xaa-Thr-Xaa-Xaa-Xaa-Arg-Pro-Val-His-Asp-Ala-Ala-Arg-Glu-Gly-Phe-Leu-Asp-Thr-Leu-Val-Val-Leu-His-Xaa-Xaa-Gly-Ala-Arg-Leu-Asp-Val-Arg-Asp-Ala-Trp-Gly-Arg-Leu-Pro-Xaa-Asp-Leu-Ala-Xaa-Glu-Xaa-Gly-His-Xaa-Asp-Xaa-Xaa-Xaa-Tyr-Leu-Arg-Xaa-Ala-Xaa-Gly-Gly-Thr-Arg-Gly-Ser-Asn-His-Ala-Arg-Ile-Asp-Ala-Ala-Glu-Gly-Pro-Ser-Asp-Ile-Pro-Asp; (SEQ ID No. 12)
or alternatively, by the sequence:
Met-Arg-Glu-Glu-Asn-Lys-Gly-Met-Pro-Ser-Gly-Gly-Gly-Ser-Asp-Glu-Gly-Leu-Ala-Thr-Pro-Ala-Arg-Gly-Leu-Val-Glu-Lys-Val-Arg-His-Ser-Trp-Glu-Ala-Gly-Ala-Asp-Pro-Asn-Gly-Val-Asn-Arg-Phe-Gly-Arg-Arg-Ala-Ile-Gln-Val-Met-Met-Met-Gly-Xaa-Xaa-Xaa-Val-Ala-Xaa-Leu-Leu-Leu-Xaa-Xaa-Gly-Ala-Xaa-Xaa-Asn-Cys-Xaa-Asp-Pro-Xaa-Thr-Xaa-Xaa-Xaa-Arg-Pro-Val-His-Asp-Ala-Ala-Arg-Glu-Gly-Phe-Leu-Asp-Thr-Leu-Val-Val-Leu-His-Xaa-Xaa-Gly-Ala-Arg-Leu-Asp-Val-Arg-Asp-Ala-Trp-Gly-Arg-Leu-Pro-Xaa-Asp-Leu-Ala-Xaa-Glu-Xaa-Gly-His-Xaa-Asp-Xaa-Xaa-Xaa-Tyr-Leu-Arg-Xaa-Ala-Xaa-Gly-Asp, (SEQ ID No. 13)
or yet in another embodiment, by the sequence:
Met-Met-Met-Gly-Xaa-Xaa-Xaa-Val-Ala-Xaa-Leu-Leu-Leu-Xaa-Xaa-Gly-Ala-Xaa-Xaa-Asn-Cys-Xaa-Asp-Pro-Xaa-Thr-Xaa-Xaa-Xaa-Arg-Pro-Val-His-Asp-Ala-Ala-Arg-Glu-Gly-Phe-Leu-Asp-Thr-Leu-Val-Val-Leu-His-Xaa-Xaa-Gly-Ala-Arg-Leu-Asp-Val-Arg-Asp-Ala-Trp-Gly-Arg-Leu-Pro-Xaa-Asp-Leu-Ala-Xaa-Glu-Xaa-Gly-His-Xaa-Asp-Xaa-Xaa-Xaa-Tyr-Leu-Arg-Xaa-Ala-Xaa-Gly-Cys-Ser-Leu-Cys-Ser-Ala-Gly-Trp-Ser-Leu-Cys-Thr-Ala-Gly-Asn-Val-Ala-Gln-Thr-Asp-Gly-His-Ser-Phe-Ser-Ser-Ser-Thr-Pro-Arg-Ala-Leu-Glu-Leu-Arg-Gly-Gln-Ser-Gln-Glu-Gln-Ser. (SEQ ID No. 14)
In preferred embodiments, the CCR-protein specifically binds a CDK, e.g. a G1 phase CDK, e.g. CDK4 and/or CDK6. The CCR-protein can be cloned from a mammalian cell, e.g. a human cell, e.g. a mouse cell.
Another aspect of the present invention features a polypeptide, of the CCR-protein family, which functions in one of either role of an agonist of cell-cycle regulation or an antagonist of cell-cycle regulation. In a preferred embodiment: the subject CCR-protein specifically binds a cyclin dependent kinase (CDK), e.g. specifically binds CDK4; e.g. specifically binds CDK6; e.g. inhibits a kinase activity of CDK4; inhibits a kinase activity of CDK6; e.g. inhibits phosphorylation of an RB protein by CDK4. In a more preferred embodiment: the CCR-protein regulates a eukaryotic cell-cycle, e.g. a mammalian cell-cycle, e.g., a human cell-cycle; the CCR-protein inhibits proliferation/cell growth of a eukaryotic cell, e.g., a human cell; the CCR-protein inhibits progression of a eukaryotic cell from G1 phase into S phase, e.g., inhibits progression of a mammalian cell from G1 phase into S phase. e.g., inhibits progression of a human cell from G1 phase into S phase; the CCR-protein inhibits the kinase activity of a cyclin dependent kinase (CDK), e.g. a CDK active in G1 phase, e.g. CDK4; the CCR-protein suppresses tumor growth, e.g. in a tumor cell, e.g. in a tumor cell having an unimpaired RB or RB-like protein checkpoint. Moreover, CCR-proteins of the present invention may also have biological activities which include: an ability to regulate cell-cycle progression in response to extracellular factors and cytokines, e.g. functional in paracrine or autocrine regulation of cell growth and/or differentiation, e.g. inhibit CDK activation in response to transforming growth factor-xcex2 (TGF-xcex2) or related growth, differentiation or morphogenesis factor.
Yet another aspect of the present invention concerns an immunogen comprising a CCR-protein of the present invention, or a fragment thereof, in an immunogenic preparation, the immunogen being capable of eliciting an immune response specific for the CCR-protein; e.g. a humoral response, e.g. an antibody response; e.g. a cellular response.
Another aspect of the present invention features recombinant CCR-protein, or a fragment thereof, having an amino acid sequence preferably: at least 60% homologous to the amino acid sequence represented in one of SEQ ID No. 2, 4 or 6; at least 80% homologous to the amino acid sequence represented in one of SEQ ID No. 2, 4 or 6; at least 90% homologous to the amino acid sequence represented in one of SEQ ID No. 2, 4 or 6; identical to the amino acid sequence represented in one of SEQ ID No. 2, 4 or 6. In a preferred embodiment: the fragment comprises at least 5 contiguous amino acid residues of SEQ ID No. 2, 4 or 6; the fragment comprises at least 20 contiguous amino acid residues of SEQ ID No. 2, 4 or 6; the fragment comprises at least 50 contiguous amino acid residues of SEQ ID No. 2, 4 or 6. In a preferred embodiment, the recombinant CCR-protein functions in one of either role of an agonist of cell-cycle regulation or an antagonist of cell-cycle regulation. In a more preferred embodiment: the CCR-protein specifically binds a cyclin dependent kinase (CDK), e.g. specifically binds CDK4; e.g. specifically binds CDK6; e.g. inhibits a kinase activity of CDK4; inhibits a kinase activity of CDK6; e.g. inhibits phosphorylation of an RB protein by CDK4. In a more preferred embodiment: the CCR-protein regulates a eukaryotic cell-cycle, e.g. a mammalian cell-cycle, e.g., a human cell-cycle; the CCR-protein inhibits proliferation/cell growth of a eukaryotic cell, e.g., a human cell; the CCR-protein inhibits progression of a eukaryotic cell from G1 phase into S phase, e.g., inhibits progression of a mammalian cell from G1 phase into S phase, e.g., inhibits progression of a human cell from G1 phase into S phase; the CCR-protein inhibits the kinase activity of a cyclin dependent kinase (CDK), e.g. a CDK active in G1 phase, e.g. CDK4; the CCR-protein suppresses tumor growth, e.g. in a tumor cell, e.g. in a tumor cell having an unimpaired RB or RB-like protein checkpoint.
In yet other preferred embodiments. the recombinant CCR-protein is a fusion protein further comprising a second polypeptide portion having an amino acid sequence from a protein unrelated the protein of SEQ ID No. 2, 4 or 6. Such fusion proteins can be functional in a two-hybrid assay.
Another aspect of the present invention provides a substantially pure nucleic acid having a nucleotide sequence which encodes a CCR-protein, or a fragment thereof, having an amino acid sequence at least 60% homologous to one of SEQ ID Nos. 2, 4 or 6. In a more preferred embodiment: the nucleic acid encodes a protein having an amino acid sequence at least 80% homologous to SEQ ID No. 2, more preferably at least 90% homologous to SEQ ID No. 2, and most preferably at least 95% homologous to SEQ ID No. 2; the nucleic acid encodes a protein having an amino acid sequence at least 80% homologous to SEQ ID No. 6, more preferably at least 90% homologous to SEQ ID No. 6, and most preferably at least 95% homologous to SEQ ID No. 6. The nucleic preferably encodes a CCR-protein which specifically binds a cyclin dependent kinase (CDK); e.g. specifically binds CDK4; e.g. specifically binds CDK6; e.g. which inhibits a kinase activity of CDK4; e.g. which inhibits phosphorylation of an RB protein by CDK4.
In another embodiment, the nucleic acid hybridizes under stringent conditions to a nucleic acid probe corresponding to at least 12 consecutive nucleotides of SEQ ID No. 1; more preferably to at least 20 consecutive nucleotides of SEQ ID No. 1; more preferably to at least 40 consecutive nucleotides of SEQ ID No. 1.
In a further embodiment, the nucleic acid hybridizes under stringent conditions to a nucleic acid probe corresponding to at least 12 consecutive nucleotides of SEQ ID No. 3; more preferably to at least 20 consecutive nucleotides of SEQ ID No. 3; more preferably to at least 40 consecutive nucleotides of SEQ ID No. 3.
In yet a further embodiment, the nucleic acid hybridizes under stringent conditions to a nucleic acid probe corresponding to at least 12 consecutive nucleotides of SEQ ID No. 5; more preferably to at least 20 consecutive nucleotides of SEQ ID No. 5; more preferably to at least 40 consecutive nucleotides of SEQ ID No. 5.
Furthermore, in certain embodiments, the CCR nucleic acid will comprise a transcriptional regulatory sequence, e.g. at least one of a transcriptional promoter or transcriptional enhancer sequence, operably linked to the CCR-gene sequence so as to render the recombinant CCR-gene sequence suitable for use as an expression vector.
The present invention also features transgenic non-human animals, e.g. mice, which either express a heterologous CCR-gene, e.g. derived from humans, or which mis-express their own CCR-gene, e.g. p16, p15 or p13.5 expression is disrupted. Such a transgenic animal can serve as an animal model for studying cellular disorders comprising mutated or mis-expressed CCR allelles.
The present invention also provides a probe/primer comprising a substantially purified oligonucleotide, wherein the oligonucleotide comprises a region of nucleotide sequence which hybridizes under-stringent conditions to at least 10 consecutive nucleotides of sense or antisense sequence of one of SEQ ID No. 1, 3 or 5, or naturally occurring mutants thereof. In preferred embodiments, the probe/primer further comprises a label group attached thereto and able to be detected, e.g. the label group is selected from a group consisting of radioisotopes, fluorescent compounds, enzymes, and enzyme co-factors. Such probes can be used as a part of a diagnostic test kit for identifying transformed cells, such as for measuring a level of a p16, p15 or p13.5 encoding nucleic acid in a sample of cells isolated from a patient; e.g. for measuring the mRNA level in a cell or determining whether the genomic CCR gene has been mutated or deleted.
The present invention also provides a method for treating an animal having unwanted cell growth characterized by a loss of wild-type CCR-protein function, comprising administering a therapeutically effective amount of an agent able to inhibit a kinase activity of a CDK, e.g. CDK4. In one embodiment, the method comprises administering a nucleic acid construct encoding a CCR protein, e.g. p16, p15 or p13.5, e.g. a polypeptide represented in one of SEQ ID Nos. 2, 4 or 6, under conditions wherein the construct is incorporated by CCR-deficient cells and the polypeptide is expressed, e.g. by gene therapy techniques. In another embodiment, the method comprises administering a CCR mimetic, e.g. a peptidomimetic, which binds to and inhibits the CDK.
Another aspect of the present invention provides a method of determining if a subject, e.g. a human patient, is at risk for a disorder characterized by unwanted cell proliferation, comprising detecting, in a tissue of the subject, the presence or absence of a genetic lesion characterized by at least one of (i) a mutation of a gene encoding a protein represented by one of SEQ ID Nos. 2, 4 or 6, or a homolog thereof; or (ii) the mis-expression of the CCR-gene, e.g. the p16, p15 or p13.5 gene. In preferred embodiments: detecting the genetic lesion comprises ascertaining the existence of at least one of a deletion of one or more nucleotides from said gene, an addition of one or more nucleotides to said gene, an substitution of one or more nucleotides of said gene, a gross chromosomal rearrangement of said gene, a gross alteration in the level of a messenger RNA transcript of said gene, the presence of a non-wild type splicing pattern of a messenger RNA transcript of said gene, or a non-wild type level of said protein. For example, detecting the genetic lesion can comprise (i) providing a probe/primer comprising an oligonucleotide containing a region of nucleotide sequence which hybridizes to a sense or antisense sequence of one of SEQ ID Nos. 1, 3 or 5, or naturally occurring mutants thereof, or 5xe2x80x2 or 3xe2x80x2 flanking sequences naturally associated with the CCR-gene; (ii) exposing the probe/primer to nucleic acid of the tissue; and (iii) detecting, by hybridization of the probe/primer to the nucleic acid, the presence or absence of the genetic lesion; e.g. wherein detecting the lesion comprises utilizing the probe/primer to determine the nucleotide sequence of the CCR-gene and, optionally, of the flanking nucleic acid sequences; e.g. wherein detecting the lesion comprises utilizing the probe/primer in a polymerase chain reaction (PCR); e.g. wherein detecting the lesion comprises utilizing the probe/primer in a ligation chain reaction (LCR). In alternate embodiments, the level of said protein is detected in an immunoassay.
Yet another aspect of the invention pertains to a peptidomimetic which binds to a CCR-protein, e.g. p15 or p16, and inhibits its binding to a CDK, e.g. CDK4 or CDK6. For example, a preferred peptidomimetic is an analog of a peptide having the sequence VAEIG(V/E)GAYG(T/K)-V(F/Y)KARD (SEQ ID No. 15), though more preferably the peptidomimetic is an analog of the hexa-peptide V(F/Y)KARD (SEQ ID No. 16), and even more preferably of the tetrapeptide KARD (SEQ ID No. 17). Non-hydrolyzable peptide analogs of such residues can be generated using, for example, benzodiazepine, azepine, substituted gama lactam rings, keto-methylene pseudopeptides, xcex2-turn dipeptide cores, or xcex2-aminoalcohols.
Other features and advantages of the invention will be apparent from the following detailed description, and from the claims. The practice of the present invention will employ, unless otherwise indicated, conventional techniques of cell biology, cell culture, molecular biology, transgenic biology, microbiology, recombinant DNA, and immunology, which are within the skill of the art. Such techniques are explained fully in the literature. See, for example, Molecular Cloning A Laboratory Manual, 2nd Ed., ed. by Sambrook, Fritsch and Maniatis (Cold Spring Harbor Laboratory Press:1989); DNA Cloning, Volumes I and II (D. N. Glover ed., 1985); Oligonucleotide Synthesis (M. J. Gait ed., 1984); Mullis et al. U.S. Pat. No. 4,683,195; Nucleic Acid Hybridization (B. D. Hames and S. J. Higgins eds. 1984); Transcription And Translation (B. D. Hames and S. J. Higgins eds. 1984); Culture Of Animal Cells (R. I. Freshney, Alan R. Liss, Inc., 1987); Immobilized Cells And Enzymes (IRL Press, 1986); B. Perbal, A Practical Guide To Molecular Cloning (1984); the treatise, Methods In Enzymology (Academic Press, Inc., N.Y.); Gene Transfer Vectors For Mammalian Cells (J. H. Miller and M. P. Calos eds., 1987, Cold Spring Harbor Laboratory); Methods In Enzymology, Vols. 154 and 155 (Wu et al. eds.), Immunochemical Methods In Cell And Molecular Biology (Mayer and Walker, eds., Academic Press, London, 1987); Handbook Of Experimental Immunology, Volumes I-IV (D. M. Weir and C. C. Blackwell, eds., 1986); Manipulating the Mouse Embryo, (Cold Spring Harbor Laboratory Press, Cold Spring Harbor, N.Y., 1986).